1. Field of the Invention
The invention relates generally to a method of storing digital information and, more particularly, to arranging information for use in controlling operational modes of the playback apparatus.
2. Description of the Background
There has been proposed a method of arranging digital information on a record medium generally involving the steps of forming the data into user symbols, distributing the user symbols over a number of successive sectors, and with each sector being provided at its beginning with synchronization symbols and header symbols. Each sector is provided with first redundancy symbols of a first symbol correcting code. The symbols of a sector are distributed over a number of first frames, each of which contains a first, fixed number of symbols. Then, second redundancy symbols of a second symbol correcting code are added to a first frame and the symbols originating from a sector are interleaved with second redundancy symbols of a first frame over a number of second frames. Third redundancy symbols of a third symbol correcting code are added to a second frame, then the symbols originating from the first frame and third redundancy symbols are bit-serially made available for storage.
A method of this kind is described in allowed U.S. patent application Ser. No. 06/714,892, filed Mar. 22, 1985, now U.S. Pat. No. 4,680,764 issued 7/14/87, and assigned to the assignee thereof, which application is incorporated herein by reference, and the method is based on the frame format that is now customarily used for the so-called "Compact Disc" system for high-quality storage of audio information. One principal advantage is that it permits a high degree of error correction. One advantage of error correction involving interleaving techniques is that the data of the frames can be subjected to error correction upon arrival, so that the relevant data processor always has a uniform work load; moreover, a comparatively small buffer capacity is required. Consequently, such system is particularly suitable for real-time applications at comparatively low costs.
According to the above-identified patent application, the known compact audio disc format can be adapted for use when other data information, for example computer software, is to be stored, however, for such applications certain masking or concealing processes or permissible non-correctable errors, which can be used for audio information, become useless. One reason for this is the lack of correlation in this nonaudio data. In these other applications adequate protection must be achieved by providing an additional level of error protection, such as a symbol correcting code mentioned above. This protection is organized sector-wise, because for such data information the real-time principle at the frame level will usually be less important and, in any event, additional storage capacity (RAM) will typically be present. In such circumstances, the Compact Disc format will still be used, because the relevant encoders/decoders are manufactured in such large numbers that they are relatively inexpensive.